Chris Schneider / AP Photo

Newt Gingrich has positioned himself as Mitt Romney's biggest threat to the nomination, but come Tuesday when Republicans in Colorado, Minnesota and Missouri come out to vote, it's Rick Santorum, not Gingrich that represents the biggest threat to Romney's winning streak. Moreover, a strong performance by Santorum in the Colorado and Minnesota caucuses will help him narrow the delegate gap with Newt Gingrich.

While we haven't seen any traditional polling in Minnesota, based on the behavior we are seeing from the Santorum and Romney campaigns, the Santorum campaign looks poised for a strong showing there. The Romney campaign has spent much of today attacking Santorum's record in the Senate - and sending former Minnesota Gov. Tim Pawlenty to that attacking- which suggests they take the Santorum threat seriously.

Furthermore, Restore Our Future, the Super PAC supporting Romney has spent $131,172 on television advertising in Minnesota and nothing in Missouri or Colorado. The Super PAC supporting Rick Santorum on the other hand- The Red, White and Blue Fund- has spent money on advertising in Missouri and Minnesota- $51,000 and $123,000 respectively.

The Gingrich SuperPAC, which spent millions on TV ads in Florida and South Carolina, has yet to spend a dime in any of these states. No phones. No mail. Nothing. In fact, it's more than likely that Gingrich's battle cry of "45 states to go" will have to be changed to "OK, so we still have 42 more chances to win a state".

Santorum is also boosted by the fact that Gingrich is not on the ballot in Missouri, which means that he doesn't have to compete for the "consensus conservative" vote with Gingrich. The good news for Gingrich, the Missouri contest is a "beauty contest" where no delegates will be awarded. Instead, delegates will be determined in state caucuses on March 17.

Romney is expected to win the Colorado caucus, but whether he'll be able to reach the 60 percent that he took in 2008 is another matter. Santorum can boast of support from influential Christian conservative leaders in Colorado Springs, like Focus on the Family's James Dobson. El Paso County, home of Colorado Springs, casts the biggest percentage of GOP votes in the state.

The big bummer for Santorum, however, is that these low-key contests won't get anywhere close to the level of coverage of the previous five contests. Reporters and cable outlets are not currently swarming the Twin Cities, St. Louis or Denver. Ultimately, that makes it harder for Santorum to get the kind of national boost that Romney and Gingrich got with their victories.